Process for the manufacture of aromatic substituted alkanes



United States Patent 3,483,262 PROCESS FOR THE MANUFACTURE OF ARO- MATICSUBSTITUTED ALKANES Husni R. Alul and Gilbert J. McEwan, St. Lou s, Mo.,assignors to Monsanto Company, St. Louis, Mo., a corporation of DelawareNo Drawing. Filed May 26, 1966, Ser. No. 553,033 Int. Cl. C07c 3/54,37/14 U.S. Cl. 260-624 10 Claims ABSTRACT OF THE DISCLOSURE Thisinvention relates to methods for the manufacture of arylalkanes andalkylphenols and more specifically,

the invention relates to methods for producing arylalkanes andalkylphenols having a relatively low content of isomers in which thearomatic substituent is in the 2 position on the alkyl chain.

It is known that sulfonates of arylalkanes and ethoxylated alkylphenolsprepared from straight chain alkenes have different properties dependingupon the position of the aromatic substituent upon the aliphatic groupand while for some applications a product containing a high percentageof compounds in which the aromatic substituent is near one end of thealiphatic chain is desirable, for most applications in the surfaceactive field arylalkane and alkylphenol products are desired containingrelatively low amounts of isomers in which the aromatic substituent isin the 2 position on the alkyl chain. When the startin alkene is one inwhich the double bond is centrally disposed in the aliphatic chain, analkylation product is usually obtained which has a relatively lowcontent of isomers in which the aromatic group is positioned near oneend of the alkyl chain but When the starting alkene is a straight chainalpha-olefin, the alkylation product normally has a content of isomersin which the aromatic substituent is in the 2 position of the alkylchain which is so high as to make the product less than most desirablefor some uses. Numerous processes have been reported for obtaining fromalpha-olefins arylalkane products containing low amounts of 2-arylalkaneisomers, but many of these processes require a separate processingoperation and, in some instances, even with the use of an added processstep, the 2-arylalkane isomer content of the product is still in excessof about to It will be seen, therefore, that a process for theproduction, from straight chain alpha-olefins, without an extraprocessing step, of a product having an exceedingly low content ofisomers in which the aromatic substituent is then in the 2 positionwould be an advance in the art.

It has now been found in accordance with this invention that in thereaction of a straight chain alpha-olefin with a monocyclic aromatichydrocarbon or a monocyclic phenol using an HP catalyst, the presence ofa parafiin material greatly reduces the quantity in the alkylationproduct of isomers in which the aromatic substituent is in the 2position. In fact, the reduction in most instances is at least as greatas that which could be obtained by subjecting the starting alkene to aseparate isomerization process and the 2-isomer content of the productclosely approaches that which could be obtained under similar conditionsusing a pure alkene material containing only the isomer in which thedouble bond is in a central position. The parafiin diluent can suitablybe added to the reactor simultaneously with the reactants and can berecovered in the distillation operation conventionally performedsubsequent to the alkylation so that the process does not require anyadditional process step and does not result in the consumption of asubstantial quantity of any additional raw material.

Any paraffin material can suitably be employed in the process of thisinvention and one can use straight chain parafiins, branched chainparaflins, or cyclo-paraflins alone or in admixture with each other.Straight chain paraflins and unsubstituted cyclo-paraflins are preferredbecause the presence of a secondary or tertiary carbon atom in theparaffin increases its reactivity in the presence of HF and can underadverse conditions result in undesired side reactions. The choicebetween straight chain paraffins and unsubstituted cyclo-parafiins isdictated largely by availability, but in some instances, the boilingpoint or solubility of the paratfin in the reactants will have a bearingupon ones choice. It is desirable that a parafiin material be selectedwhich has a boiling point different from that of the aromatic reactantused in the manufacture of the arylalkane product and different fromthat of any of the isomers normally present in the reaction product sothat the parafiin material can readily be recovered for reuse bydistillation. Also, it is desirable to select a paraifin material thatis readily soluble at the selected level of use in the raw materialmixture and also in the individual reactants so that the formation of aseparate parafiin phase is avoided. The latter consideration presents noreal problem since almost all paraffin materials are miscible with theusual alkenes and aromatic hydrocarbons utilized in the production ofarylalkane and alkylphenol detergent intermediates.

The chain length or number of carbon atoms in the paraflin material isof little or no importance as long as the paraffin material has thedesired physical characteristics because, as set forth above, theparafiin is normally inert in the reaction mixture and is recoveredunchanged upon the completion of the reaction. Generally, a paraflinshould be selected which has a boiling point at least as high as themaximum reaction temperature to be employed but not so high that itcannot be recovered from the high boiling still bottoms by distillation.Similarly, as set forth above, a chain length can be selected to providea boiling point different from that of the unreacted raw material andany of the desired isomers of the product to facilitate recovery of theparaflin material. If the reaction is to be conducted at a very lowtemperature and/or under pressure, it is possible to employ a materialhaving as few as 4 carbon atoms such as nbutane or cyclobutane. At theother extreme, it is pos sible to employ paraffins having as many asabout 32 carbon atoms as illustrated by petroleum waxes although in someinstances solubility and recovery problems are encountered whenemploying such materials. Normally, it is preferred to use a paraflinmaterial having from 5 to 15 carbon atoms and illustrative examples ofpreferred materials include n-hexane, cyclo-hexane, n-heptane, andn-dodecane.

Within limits, the amount of paraffin employed has a bearing upon thequantity of 2-arylalkanes or 2-hydroxyarylalkanes in the alkylationproduct and if one desires only a slight reduction in the content ofsuch isomers in the product, it is only necessary in accordance Withthis invention to employ as little as about 5% by weight, based upon theweight of alkene reactant, of parafiin. In most instances, however, onewill desire a relatively large reduction in the 2-arylalkane or2-hydroxyarylalkane isomer content of the reaction product and willemploy an amount of paraffin equal to at least about 50% by weight,based upon the weight of alkene reactant. It is seldom, if ever,advantageous to employ the paraffin material in an amount such that theweight ratio of parafiin to alkene is more than about 10:1 since the useof more than this amount of parafiin does not give a correspondingreduction in the Z-arylalkane or 2-hydroxyarylalkane isomer content ofthe product, necessitates the handling of larger quantities of materialsand, in addition, increases the cost of product and parafiin recovery.However, except for these disadvantages, the addition of large excessesof parafiin is not objectionable and satisfactory results can beobtained using, for example, a weight ratio of parafiin material toalkene of 50 to 1. In most instances, the preferred amount of paraffinmaterial to be employed is from about 100% to 1000% by weight, basedupon the weight of alkene reactant or, in other words, a weight ratio ofparaflin to alkene of from about 1: 1 to about 1021.

In accordance with a preferred embodiment of the invention, the parafiinmaterial is divided into two quantitles and a first portion thereof ismixed with at least a portion of the aromatic reactant, for example from10% to 100% thereof, and the desired quantity of HF catalyst. The secondportion of the parafiin material is then mixed with the alkene reactantand the remainder, if any, of the aromatic reactant. The two mixturesare then mixed together over a period of time preferably with constantagitation to eliminate the possibility of localized concentration ofreagents and undesired temperature gradients within the reactionmixture. Normally, it is desirable that the portions of the paraffinmaterial be approximately equal, and if the paraffin is divided intounequal proportions, the larger proportion should be added to thecatalyst containing mixture before the alkene is mixed therewith.Preferably, from about 40% to 90% by weight of the parafiin should beadded to the catalyst containing mixture but satisfactory results can beobtained by adding 100% of the paraflin to the catalyst mixture or anyother percentage as long as the catalyst mixture contains an amount ofparatlin equal to about by weight of the alkene reactant at the timemixing of the alkene reactant with the catalyst is initiated.

Except as set forth above, the process of this invention can beconventional and can be employed in the production of substantially anyarylalkane or alkylphenol product which has been conventionally employedin the manufacture of detergent surface active agents. The aromatichydrocarbon most frequently employed in the manufacture of detergentintermediates is benzene, and the phe nolic compound most frequentlyemployed is phenol. However, other monocyclic aromatic hydrocarbons andphenols can suitably be employed in the process, and suitable examplesinclude resorcinol, ortho-cresol, toluene, xylene, and cumene. Anyaliphatic hydrocarbon substituent group or groups on the aromaticnucleus should in each instance be saturated to prevent side reactionsand the total number of substituents, including hydroxy groups, on thearomatic nucleus preferably should not be more than 2 or 3 in number. Inmost instances, the aromatic reactant will contain not more than about 9carbon atoms, although this limitation is dictated by availability anddesirability for use in the manufacture of detergent intermediates, andif desired, the invention can be used with aromatic reactants containing12 or 15 or more carbon atoms.

Straight chain alpha-olefins which can suitably be em ployed in theprocess of this invention include any of those conventionally employedin the manufacture of detergent intermediates. In most instances, thealpha-olefins will have from 8 to 24 carbon atoms, and alpha-olefinshaving a molecular chain length of from to 20 carbon atoms arepreferred. Commercial alpha-olefins are usually mixtures rather thansubstantially pure materials and such mixtures having average molecularchain lengths within the above ranges are quite suitable for use in theprocess of this invention.

As in conventional practice, it is usually advantageous in accordancewith this invention to employ an aromatic to olefin molar ratio of atleast about 1:1 because the use of a lower ratio results in excessiveformation of high boiling by-products. There is no upper limit as to thearomatic to olefin molar ratio except that dictated by convenience andthe economics of recovering unreacted raw materials, and an aromatic toolefin ratio as high as 100:1 can suitably be employed, but thepreferred aromatic to olefin ratio is generally from 1 /2:1 to 10:1.Varying the aromatic to olefin ratio in most instances has no markedeffect upon the Z-arylalkane or 2-hydroxy arylalkane content of theproduct but does affect in a conventional manner the nature and amountof by-products produced.

The amount of catalyst to be employed can be conventional and can rangefrom about 10% by weight, based upon the weight of alkene material inthe reaction mix: ture, to an upper limit dictated only by convenienceand one can, for example, with satisfactory results, employ an amount ofcatalyst sufiicient to provide a weight ratio of catalyst to totalolefin of as high as 20: 1. If desired, one can even employ inaccordance with the procedure described and claimed in United Statesapplication, Ser. No. 553,030, filed concurrently herewith, such a smallamount of catalyst, for example, as little as 0.2% by weight based uponthe over-all weight of the reaction mixture, that a separate catalystphase is not obtained, but this results in a marked increase in the2-arylalkane isomer content of the product as compared to the minimumwhich can be obtained employing the process of the present invention andin most instances is not desirable. In most instances, a preferredamount of catalyst is that which will provide a weight ratio of catalystto total olefin reactant of from 1:2 to 10: 1.

The temperature at which the reaction is conducted in accordance withthis invention can be conventional, and for example, can range from thefreezing point of the reaction mixture to about 200 C. or even higher,but the preferred operating temperature range is from about 10 C. to C.with temperatures of from about 5 C. to 60 C. being especiallypreferred. A change in operating temperature in most instances resultsin a significant change in the proportion of 2- arylalkane orZ-hydroxyarylalkane isomers in the product with low reactiontemperatures favoring decreased amounts of the 2-arylalkane orZ-hydroxyarylalkane isomers in the product. For example, it has beenfound that a reduction in temperature of from 55 C. to 0 C. can in someinstances result in a much as 7% to 8%, based on the over-all weight ofthe product, reduction in the percent of Z-phenyl isomers in theproduct.

The pressure under which the alkylation reaction is conducted can bevaried within a wide range as long as the pressure employed is not solow as to result in the vaporization of raw materials or excessivecatalyst loss. Suitable operating pressures can vary from about 0.5 to10 atmospheres with the preferred pressure range being from about 1 to 4atmospheres.

The invention will now be illustrated by the following specific examplesin which all parts are by weight unless otherwise indicated:

EXAMPLE I (A) A mixture of 200 parts of benzene and 200 parts by weightof anhydrous HP is placed in a suitable alkylation apparatus and heatedat 55 C. under 40 pounds p.s.i.g. pressure. At a temperature of 55 C.,it has been found that the pressure should be maintained at least about40 p.s.i.g. to avoid catalyst loss. A mixture of parts of alpha-dodeceneand 100 parts of benzene is then added with constant agitation over aperiod of ten minutes, and the reaction mixture is retained for anadditional ten minutes at 55 C. with constant agitation. The mixture isthen cooled to 6 C. and allowed to stand for one hour after which timethe organic layer is separated from the catalyst layer by decantation.The separated organic layer is then distilled to remove unreactedbenzene and dissolved HF catalyst and a sample of the thus purifiedproduct is analyzed by vapor phase chromotography to determine theisomer distribution.

(B) The procedure of A above is repeated except that 800 parts by weightof n-hexane are added to the mixture of HF and benzene, and 200 parts byweight of n-hexane are added to the mixture of alpha-dodecene andbenzene.

(C) The procedure of B above is repeated except that in place ofa weightratio of paraffin to olefin of 10:1, a weight ratio of paraflin toolefin of 50:1 is utilized.

In actual tests of the above procedures, the following results wereobtained:

Procedure B Procedure For comparative purposes, the procedures of thisexample were used to alkylate benzene with dodecene-6 and even startingwith an olefin in which the double bond is centrally disposed, it wasonly possible to reduce the 2-phenyldodecane content of the product to13.6% (14.8% when no n-hexane was employed), thus illustrating that theprocess of this invention makes possible using pure alpha-olefins ormixtures of alpha-olefins and internal olfeins, results which wereheretofore obtainable in a single step process only by using a pureolefin material in which the double bond is centrally disposed withrespect to the aliphatic chain.

EXAMPLE II Z-phenyl 12.0 11. 4 3phenyl 13. 7 14. 0 4-phenyl 19. 8 18. 65- and G-phenyl 54. 5 56. 0

By comparing the results obtained in Example I with those obtained inExample II, it will be seen that improved results are obtained using lowreaction temperatures.

EXAMPLE III (A) A mixture of 200 parts by weight of benzene and about200 parts of anhydrous HF is placed in a suitable alkylation apparatusand heated to 55 C. maintaining a pressure of 40 p.s.i.g. to insure thepresence of a liquid HF phase. There is then added to the catalystmixture over a period of about ten minutes and with constant agitation amixture containing 25 parts by weight of alphadodecane, 25 parts byweight of alpha-tetradecene, 25 parts by weight of alpha-hexadecene, 25parts by weight of alpha-octadecene, and 100- parts by weight ofbenzene. Stirring is then continued for at least about ten additionalminutes, and the mixture is cooled to 6 C. and allowed to stand for onehour. The organic layer is then separated and distilled to removeunreacted benzene and dissolved HF catalyst and a sample of the thuspurified product is analyzed by vapor phase chromotography to determinethe isomer distributions of the various alkylbenzenes.

(B) An alkylation reaction is conducted substantially as described in Aabove except that to the catalyst mixture there is added prior to theinitiation of the reaction Procedure A Procedure B (non-hexane)(n-hexaue added) Percent Isomer C14 C10 C18 C14 Cw Cra Z-pheuyl Theprocedure when employing other paraffins, aromatic reactants andalpha-olefins can be the same as illustrated in the above examples.

What is claimed is:

1. In a process for the manufacture of aromatic substituted alkaneswherein an aromatic compound is reacted With an alkylation agentconsisting essentially of a straight-chain alpha-olefin of from about 8to 24 carbon atoms in the presence of hydrogen fluoride catalyst, saidaromatic compound being selected from the group consisting of monocyclicaromatics having not more than 15 carbon atoms and in which the aromaticnucleus has not more than three substituents, the substituents in eachinstance being selected from the group consisting of hydroxy and alkylgroups, the improvement which comprises increasing the proportion of theproduct wherein the aromatic substituent occupies a position other thanthe 2 position on the alkyl chain by performing said reaction in thepresence of a paraflin having from about 4 to 32 carbon atoms, theamount of said parafiin present in the reaction mixture being at least5% by weight, based on the weight of alpha-olefin reactant, but not inexcess of the solubility of the paraffin in the organic phase of thereaction mixture and not in excess of a weight ratio of paraffin toolefin of about 50:1, said reaction being performed at a temperature offrom the freezing point of the reaction mixture to 200 C.

2. A process in accordance with claim 1 wherein said alpha-olefin has amolecular chain length of from 10 to 20 carbon atoms.

3. A process in accordance with claim 1 wherein the reaction temperatureis within the range of about -10 C. to C.

4. A process in accordance with claim 3 wherein the amount of hydrogenfluoride catalyst in said reaction mixture is maintained at a levelsufficient to provide a separate liquid catalyst phase throughout thereaction period.

5. A process in accordance with claim 4 wherein said paraflin is astraight chain paraffin having from 5 to 15 carbon atoms.

6. A process in accordance with claim 5 wherein said aromatic compoundis benzene.

7. A process in accordance with claim 5 wherein said aromatic compoundis phenol.

8. A process in accordance with claim 6 wherein said parafiin isn-hexane.

9. A process in accordance with claim 1 wherein a first mixture isformed of at least a portion of said aromatic compound, said H.F.catalyst, and a portion of said paraffin, a second mixture is formed ofsaid alkene reactant, the remainder, if any, of said aromatic compoundand a portion of said paraflin, and said mixtures are then mixedtogether while maintaining the temperature of the resultant mixturewithin the range of -10 C. to 80 C. and while maintaining the resultantmixture under a pressure of from 0.5 to 10 atmospheres correlated withrespect to temperatures to prevent catalyst loss.

10. A process in accordance with claim 9 in which the 7 8 temperature ofthe reaction mixture is maintained in the 2,943,118 6/ 1960 Cahn et a1260-671 range of 5 C. and 60 C. 3,275,702- 8/1963 :Hutsqn 1 26067-1References Cited UNITED STATES PATENTS 2,051,473 8/ 1936 Evans et a1260-624 2,351,347 6/1944 Luten 25252 6 2,874,193 2/1959 Dijkstra 260-624260-4571 3,349,144 10/1967 A1111 et a]. 260 671 BERNARD'HELFIN, PrimaryExaminer W. B. LONE, Assistant Examiner U.S. c1. X.R.4

